Okay a kid I know just bought an 89 N/A, he has been having problems with the idle. I first tried to adjust the idle with the tiny screw on the throttle body. But since I have only worked on my car, an 87 TII, I could not find it. So my first question is where is the adjustment screw for idle. On my car if you are standing on the passenger side of the engine bay and look on the left side of the UIM at the throttle body it is right on the actual mechanism that regulates throttle position. Is this adjustment screw in the same location, or is it in a different location. Or am I just having trouble seeing it. Secondly on the top of the intake manifold there is a screw which he said controls vacuum. So he randomly began loosening and tightening it, to see what the idle would do. My immediate reaction was to tell him to stop and leave it where it was until we found out what it actually does, and how to go about adjusting it. Unfortunately he didn't listen . So what does this screw control? Does it affect idle? And if so how so you go about adjusting it? I wanted to check the TPS but neither of us has a volt detector thing, sorry I can't remember what it actually is right now. So if anyone would help answer some of these questions it would be most appreciated. I did a search but was unable to find the specific answers that I am searching for. If you find something in search please let me know and I apollogize for not seeing it if you find it. Thanks for the help.

- Steiner

 

FOr the S5, the only idle adjustment you have (aside from the throttle stop) is that screw on top of the TB under the rubber cap.

You got to jumper the ISC to make these adjustments.

Jarrett

 

If you do not install the jumper the ECU tries to compensate for the adjustment of the screw under the black rubber cap.

That is the same jumper you use when reading the ECU fault codes. Check those also.

Good luck.

 

Okay I'm completely confused now, because I've never worked on an N/A before, where the hell is this screw with a black cap on it. And I just searched ISC, and first of all j rat I think you were in every thread I looked at, second of all, I learned nothing from reading that stuff. I still don't know where it is, or how to jump it, I looked at the FSM under Engine Electrical and didn't see anything relating to idle adjustement aside from the CAS, and I didn't see the ISC in there either. So maybe if you could give me a more dumbied down version I will be able to understand this, and then fix it. Sorry for not knowing this stuff guys.

- Steiner

 

"top of the intake manifold there is a screw which he said controls vacuum" this should be under a black rubber cap or cover.
Go to FSM (in 1991) page F1-16 or last page of engint tune-up there are pictures of test connector and idle air adjust screw.
You need to make a jumper wire.
Be sure to remove jumper wire when pau.